This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In the last ten years influenza carried by birds has taken a worldwide stage as a zoonotic pathogen with potentially devastating effects on world health (Holmes et al., 2005). Migratory birds, implicated in the spread of Asian H5N1 influenza, cover vast distances twice a year, coming into contact with a wide range of habitats, many of them part of human habitats. While a great deal of work remains focused on common human subtypes of influenza which cause thousands of deaths worldwide each year, it is now realized that many of the common strains in humans and other animals may have derived from the vast pool of viruses circulating in wild birds. Unfortunately, despite years of surveillance in wild birds the scientific community understands very little about the natural history and ecology of infection and transmission in wild birds (Causey and Edwards, 2009). The ecology of the influenza virus encompasses a broad understanding in three realms: 1) the transmission of virus in space and time between individuals (epizootiology) 2) the biogeochemical environment in which the virus resides and 3) the host-pathogen interface (encompassing the dynamics of infection within the avian host). To understand the ecology of the virus in the natural world, we must understand the epizootiology of the virus in host populations (current focus of research). However, the epizootiology of influenza is likewise influenced directly by the dynamics of viral infection within the host. In the natural world, we expect the dynamic of infection could be strongly modified by the biological and biogeochemical environment of the host and the virus that gains entry to that host. In the natural world, the dynamics of infection in potential contact zones with humans includes the potential effects of co-infection with other zoonotic pathogens and with toxicants.